Superelastic stability of nanocrystalline Ni47Ti50Fe3 shape memory alloy
Taotao Wang, Fangmin Guo, Taotao Ai, Yapeng Li
Abstract
NiTi shape memory alloys have been widely explored because of their superelasticity. However, the application of conventional coarsed NiTi SMAs is limited by low superelastic stress and poor superelastic stability due to their low yield strength. In this study, nanocrystalline (NC) Ni 47 Ti 50 Fe 3 alloy with average size is ∼15 nm was obtained by large deformation cold drawing and low temperature annealing. After ten cycles of loading (up to 6%)-unloading, the NC Ni 47 Ti 50 Fe 3 alloy exhibited a high superelastic stress (1170 MPa)，low areduction rate of superelastic stress (12%) and small residual strain (0.66%). This overall performance is better than that of previous NiTi-based SMAs. We have suggested that this mainly stems from the synergistic reinforcement combines Fe element doping and high-density grain boundary.